1. Technical Field
The present disclosure relates generally to communication networks and more particularly to pseudowire configurations in communication networks.
2. Description of Related Art
Virtual Private Network (VPN) services provide secure network connections between different locations. A company, for example, can use a VPN to provide secure connections between geographically dispersed sites that need to access the corporate network so that each customer edge (CE) end point or node can communicate directly and independently with all other CE nodes. Different types of VPNs have been classified by the network layer used to establish the connection between the customer and provider network. For example, Virtual Private LAN Service (VPLS) is an architecture that delivers a multipoint Layer 2 VPN (L2VPN) service that in all respects emulates an Ethernet Local Area Network (LAN) across a wide metropolitan geographic area. All services in a VPLS appear to be on the same LAN, regardless of location. In other words, with VPLS, customers can communicate as if they were connected via a private Ethernet segment, i.e., multipoint Ethernet LAN services.
In this context, each CE device at a customer site is connected to the service provider network at a provider edge (PE) device by an Attachment Circuit (AC) that provides the customer connection to a service provider network, that is, the connection between a CE node and its associated PE node. Within the provider network, each PE device includes a Virtual Switch Instance (VSI) that emulates an Ethernet bridge (i.e., switch) function in terms of Media Access Control (MAC) address learning and forwarding in order to facilitate the provisioning of a multipoint L2VPN. A pseudowire (PW) is a virtual connection between two PE devices that connect two attachment circuits. In the context of the VPLS service, a pseudowire can be thought of as a point-to-point virtual link for each offered service between a pair of VSIs. Therefore, if each VSI can be thought of as a virtual Ethernet switch for a given customer service instance, then each pseudowire can be thought of as a virtual link connecting these virtual switches to each other over a Packet Switched Network (PSN) for that service instance.
Since the failure of pseudowires obviously degrades network performance, some effort has been directed towards adding system redundancies including redundant pseudowires. However, the presence of redundant pseudowires alone is insufficient to improve overall failover performance, that is, the ability to switch over automatically to a redundant or backup system. Thus, there is a need for improved methods for managing pseudowires to facilitate pseudowire switching and enable improved failover performance.